Tip for electric weft detectors



Oct. 29, 1940. o. v. PAYNE 2,

TIP FOR ELECTRIC WEFT DETECTORS Filed Sept. 25, 19:59

.. 13mg; l

INVENTOR OscARV. PAYNE ATTORNEY elements.

Patented Oct. 29, 1940 UNITED STATES TIP FOR ELECTRIC WEFT DETECTORS Oscar V. Payne, Leicester, Maser, assignor to Crompton & Knowles Loom Works, Worcester, Mass, a corporation of Massachusetts Application September 25, 1939, Serial No. 296,402

9 Claims.

This invention relates to electric weft detectors for looms and it is the general object of the invention to provide a resilient electric current conducting feeler tip for the detector elements.

Electric weft detectors ordinarily employ two detector elements connected to opposite sides of an electric loom controlling circuit and mounted in a support which insulates them from each other. The bobbin which cooperates with the detector has a metallic ferrule ordinarily covered with weft which prevents electric contact of the detector elements when sufficient yarn for continued weaving is present. When weft exhaustion approaches, however, the metallic ferrule is uncovered and electrically connects the detector elements, whereupon the control circuit brings about a change in the loom operation, such as replenishment.

As exhaustion approaches a thin layer of thread covers the ferrule and if any of these threads should be so located as to be struck by one or another of the detector elements as the lay moves forwardly there is danger of thread breakage, and this is particularly true where the weft is very fine yarn. The ferrule on the bobbin is metallic and the ends of the detector elements are also metallic and the inertia of the elements as heretofore constructed has been suflicient to strike the Weft a damaging blow should it lie between the ferrule and a detector element.

It is an important object of my present invention to provide the detector elements with ferrule engaging tips so constructed as to yield before the detector elements start to move forwardly, thereby subjecting the weft thread to a blow considerably less than would be the case if the detector element were rigid throughout its length and were required to move as soon as contact with the weft was established.

A form of electric Weft detector which has gone into extensive use is that shown in my prior Patent No. 1,924,197 the insulated detector elements of which are each surrounded by a light spring holding the elements yieldingly in rearward position for contact with the bobbin. The detector shown in that patent requires that the bobbin transmit to the detector elements through the yarn engaging them sufficient force to overcome the inertia of the elements and also the yielding resistance offered by the springs surrounding the It is a further object of my present invention to provide the detector elements with tips which will yield under a force less than that required to overcome the inertia of the elements and the resistance of their springs.

The tip may conveniently be in the form of a coil spring the axis of which is the same as that of the element on which it is mounted and constructed with adjacent coils slightly spaced so that at the instant of impact with the bobbin the coils can be compressed and thereby subject the .yarn

to a light force which gradually increases as the tip coils approach each other until sufficient to move the detector element forwardly. In this way the blow which the feeler tip strikes the yarn on the ferrule is considerably lowered and thread breakage is reduced.

When a detector element which is rigid throughout its length, such as that shown in my previously mentioned patent, is struck by the ferrule on the bobbin it tends to bound away from the ferrule immediately after initial contact therewith and is then returned to contact with the ferrule by the spring surrounding it. The electric contact is therefore momentarily interrupted and the total length of time for establishing the loom controlling circuit is slightly less than the time during which the ferrule is in position by motion of the lay for contact with the detector element. Another object of my invention is to provide a feeler tip for an electric weft detector constructed with an electric current conducting yieldable material which will maintain continuous contact with the bobbin ferrule throughout the detecting period and without tendency to rebound from the ferrule upon first should an abnormally placed bobbin cause sidewise bending of the feeler tip spring. The position of the rod end relatively to the tip may be determined and maintained by a small notch in the rod to receive one of the coils of the feeler tip. 7

All of the foregoing objects are achieved as set forth hereinafter by the use of a coil wire feeler tip but I do not wish to be limited to a tip of that particular form inasmuch as it is sufflcient'for certain features of my invention if the feeler tip be made of yieldable material which is also current conducting, so that force to move the detector element is imparted thereto gradually and the tip remains in continuous contact with the .ferrule as described.

With these and other objects in view which will appear as the description proceeds, my invention resides in the combinatiton and arrangement of parts hereinafter described and set forth.

In the accompanying drawing, wherein a convenient embodiment of my invention is set forth,

Fig. 1 is a plan view of a weft detector having my improved feeler tip applied thereto,

Fig. 2 is a vertical section on an enlarged scale on line 2-2, Fig. l,

Fig. 3 is an enlarged side elevation of a weft detector element equipped with my improved feeler tip, and

Fig. 4 is a vertical section on line 4-4 of Fig. 1 on an enlarged scale showing the behavior of the feeler tip when in contact with a bobbin.

Referring to the drawing, I have shown a bobbin B having a metallic ferrule F around which is wound the weft thread W. When the weft is almost exhausted single separated turns remain wrapped around the ferrule and may be struck by the detector tips with resultant breakage. The weft detector comprises a base I formed of insulating material mounted on a fixed part of the loom L and having two spaced parallel bores II and I2 extending horizontally therethrough in a direction toward and from the bobbin. Through each bore extends a detector element I3 formed as a rigid rod or wire the rear part of which extends through a slide bearing I4 in the support Ill. The forward part of the rod I3 is surrounded by a comparatively light compression spring I5 andextends through a contact member I6 to have sliding contact therewith and threaded into the corresponding bore. A nut II on each bearing engages a contact plate I8 thereby establishing electric contact between the plate and the bearing. The bearings of both bores are substantially the same and their contact plates are attached to wires I9 and 20, respectively, which extend to an external control circuit well understood and not set forth herein.

That part of the weft detector and the bobbin 'cooperating'therewith already described may be other the wires I9 and 20 are disconnected and the control circuit is open, but upon connection between the rods I3 being established by the uncovered ferrule F the circuit is closed to bring about loom stoppage or weft replenishment.

In carrying my present invention into effect I provide each of the rods I3 with an electric current conducting yieldable tip designated generally at '1. As shown in the drawing this tip is formed of light wire coiled on itself and having closed coils 30 the internal diameter of which is slightly less than the diameter of the rod I3 so that the latter will be tightly gripped by the coils 30 to hold the tip in position. Extending rearwardly from the closed coils 30 are other open coils 3I of varying diameters to form a cone as shown for instance in Fig. 3, where the convolution of largest diameter is designated at 32.

The rearmost of the open coils designated at 33 is of less diameter than the coil 32 and has the end 34 thereof turned inwardly as shown in Fig. 3 to lie in front of the plane of the coil 33 where it cannot contact the bobbin or the weft thereon. The feeler tip is made of any appropriate material, such for instance, ashard drawn phosphor bronze wire, having good current conducting qualities and not affected appreciably by oxidation. Each of the detector element rods I3 is provided with atip similar to that shown in Fig. 3, the open coils projecting beyond the rear end of the rod elements I3 to permit forward compression of the latter.

The detecting operation ordinarily occurs on the forward beat of the lay at which time the bobbin is moved toward the detector rods which are stationary due to the fact that the stand I0 is mounted on a fixed part of the loom. When contact is first established between the bobbin and the tips T as shown in full lines in Fig. 4 by impact with the coil 33 the latter moves forwardly with the bobbin and imparts motion to the coils in front of it. The coils of larger diameter bend more easily than do the smaller coils behind them and serve as a cushion to absorb the initial blow attending contact between the ferrule and the small coil 33. The force exerted between coil 33 and the ferrule as the lay advances increases gradually because of the fact that the coils in front of coil 33 are larger than the latter. The actual force exerted on any yarn which may lie between the ferrule and coil 33 is determined very largely by the force required to compress the largest and most easily compressed coil together with the inertia of the small coils behind them, this latter however, being negligible. As the lay advances more and more forward force is exerted on the rods I3 and when the open coils become ultimately temporarily closed, as indicated in dotted lines, Fig. 4, said rods are moved forwardly against the action of springs I5 by a force transmitted positively from the ferrule through the feeler tips to the dot and dash position shown in Fig. 4.

The element I3 does not start to move forwardly until an appreciable time after electric contact has been established between the ferrule and the coil 33 and during the forward motion of the' lay after impact the ferrule advanceswith a decreasing speed. The detector elements therefore do not acquire the speed of the lay until some time after electric contact has been established and at a time when the speed of the lay is approaching zero. The force therefore which must be transmitted through the weft thread to move the detector element I3 forwardly is less than in former constructions.

The bobbin will occasionally be above its normal position when presented to the detector due to improper boxing of the shuttle. Under these conditions the feeler tip is subjected to a side thrust tending to deform it. In order to protect the tip I project the end of rod I3 into the open coil section of the tip as indicated in Fig. 3 so that the distance between it and the coil 33 is slightly more than the amount of compression of the open coils when struck by the bobbin. This relation is determined and maintained by a small notch 35 in rod I3 into which one of the small closed coils 30 is driven, preferably the foremost of said coils. The rod I3 therefore protects the feeler tip against damaging lateral deformation when struck by a misplaced bobbin.

I find that there is a negligible tendency for the coil 33 to rebound away from the ferrule with the result that the latter remains in contact with the tip continuously from the first impact therewith until moved away therefrom by backward motion of the lay. I find also that a very fine weft thread can be subjected to repeated impacts to the coils 33 without breaking.

From the foregoing it will be seen I have provided a weft detector having a feeler tip formed of resilient electric conducting material and that the form set forth comprises a coil spring the axis of which is substantially perpendicular to the surface being detected. It will furtherbe understood that at the first impact with the ferrule the spring forming the feeler tip compresses before the detector rod I3 starts to move forwardly, thereby reducing shock to the weft. It will also be seen that the tip is formed with an integral cylindrical or gripping portion which surrounds the feeler rod l3 and is the means by which the latter is attached to the resilient tip. Furthermore, the open coils of the feeler tip compress more easily than do the coils of the spring l5 and this relation permits a gradual building-up of the force required to overcome the spring [5 after initial engagement between the ferrule and the coil 33 of the feeler tip. Another feature resides in the fact that the coil 33 which is near the ferrule is of smaller diameter than certain other coils such as 32 which are farther from the ferrule and this variation in diameter tends to produce a more uniform pressure between the coil 33 and the ferrule and also serves as a shock absorber for coil 33, thereby permitting the latter to remain in contact with the ferrule without appreciable rebounding. Again, the rod I3 projects into the hollow tip far enough to support the open coils should the bobbin be misplaced. While I have set forth the advantages of a feeler tip formed of a coil spring of conical form, I do not wish necessarily to be limited to a spring of this form, as certain advantages of my invention are not dependent on a feeler tip of that form.

Having thus described my invention it will be seen that changes and modifications may be made therein by those skilled in the art without departing from the spirit and scope of the invention and I do not wish to be limited to the details herein disclosed, but what I claim is:

1. A feeler tip for a metallic weft detector rod comprising a compressible spring formed of open coils of electric conducting resilient wire secured to the rod and having the rearmost coil placed for direct engagement with a surface to be detected, said coils having their axes substantially perpendicular to the surface to be detected, the coils being compressible by a force directed toward the rod, while the latter remain stationary.

2. A feeler tip comprising a spring formed of open coils of electric conducting wire wound in a generally conical form with the smaller end of the spring toward the surface to be detected with the rearmost coil placed for direct engagement with said surface and with the axis of the spring extending forwardly from the surface to be detected, the coils being compressible by a force directed toward the rod, while the latter remains stationary.

3. A detector element for an electric weft detector comprising a metallic rod and a coil of current conducting wire having certain coils surrounding and gripping one end of the detector rod by reason of their resilience and having other spaced coils projecting beyond the end of the detector rod with the rearmost of the spaced coils placed for direct engagement with the surface to be detected.

4. A detector element for an electric weft detector comprising a metallic rod having on one end thereof a metallic coiled spring formed with open coils, the distance between the coil most remote from the rod and said end of the rod being greater than the aggregate length of the spaces between the open coils.

5. In an electric weft detector including an insulating mounting in which slides an electric current conducting a detector element held yieldingly in detecting position by a resilient member, that improvement which comprises an inherently resilient electric conducting feeler tip on the rear of the feeler element, the rear end of said tip positioned for direct engagement with a surface to be detected and compressible under a forwardly exerted force by said surface less than that required to cause yielding of the resilient member.

6. In an electric weft detector having an insulating base in which slides a detector element normally held yieldingly in rearward detecting position by a resilient member, that improvement comprising a tip on the rear of the detector element formed of coils of metallic wire certain coils of which are spaced and the rearmost coil is positioned for direct contact with the surface being detected, said coils yielding under impact with said surface to be detected by a force less than that required to cause yielding of the resilient member.

7. A feeler element for a weft detector which cooperates with a mass of weft having thereunder a metallic surface to be exposed as weft exhaustion approaches, said feeler element comprising a rigid rod extending forwardly from the weft mass, and a current conducting resilient wire having thefront part thereof supported by and in electrical contact with the rod, the rear part of the wire being formed in open coils the rearmost of which is positioned for direct engagement with the weft supply, the latter acting during a detectin operation of the loom to compress the coils and thereafter exert a force through the compressed coils to initiate forward movement of the rod.

8. A feeler element for a weft detector which cooperates with a mass of weft having thereunder a metallic surface to be exposed as weft exhaustion approaches, said feeler element comprising a rigid rod extending forwardly from the weft mass and resisting forward motion, and an electric current conducting wire having the forward end thereof secured to and in electrical contact with the rod, the rear part of the wire being formed into open coils of different diameters, the rearmost coil being of less diameter than certain of the coils in front thereof and being positioned for direct engagement with the weft supply, the resistance to compression of the coils being so related to the resistance to forward motion of the rod that the weft supply compresses the coils before being able to exert a force through the compressed coils to effect forward motion of the rod.

9. In an electric weft detector for a loom having a weft supply which moves forwardly on the detecting beat of the loom and uncovers a metallic surface as weft exhaustion approaches, a metallic rod extending forwardly from the weft supply and movable in a forward direction by a force derived from the weft supply, and an electric current conducting wire secured to the rear part of the rod and projecting behind the rod and formed into open compressible coils the rearmost coil of which is positioned for direct engagement with the weft supply as the latter advances on at detecting beat of the loom, the weft supply when advancing compressing the coils and gradually setting the rod into forward motion by a forcetransmitted through the compressed coils.

OSCAR V. PAYNE. 

